title: Isolation and Characterization of Derivative Lines of the Onion Yellows Phytoplasma that Do Not Cause Stunting or Phloem Hyperplasia.
abstract: ABSTRACT Two lines of onion yellows phytoplasma producing milder symptoms were isolated from the original line (OY-W). One has an additional characteristic, non-insect-transmissibility (OY-NIM), compared with the other (OY-M). OY-M was established after maintaining OY-W for 11 years on a plant host (Chrysanthemum coronarium) with an insect vector (Macrosteles striifrons), and OY-NIM was isolated after subsequent maintenance of OY-M in plants by periodic grafting. Polymerase chain analysis suggested that OY-NIM cannot traverse the gut or survive in the hemolymph of the leafhopper. OY-W results in witches'-broom formation and stunted growth in the host plant. In contrast, OY-M and OY-NIM do not cause stunting in the host plant, although they result in witches'-broom. Histopathological analysis of these lines revealed that the hyperplastic phloem tissue and severe phloem necrosis seen in OY-W did not exist in OY-M and OY-NIM. This was attributed to a reduction in the population of phytoplasma in tissues in both OY-M- and OY-NIM-infected plants. The results suggest that the cause of stunting and phloem hyperplasia may be genetically different from the cause of witches'-broom. Pulsed field gel electrophoresis analysis showed that OY-M had a smaller genome size ( approximately 870 kbp) than OY-W ( approximately 1,000 kbp). Thus, some of the OY-W genes responsible for pathogenicity may not be present in OY-M.
authors.forename: K
authors.initials: K
authors.lastname: Oshima
authors.forename: T
authors.initials: T
authors.lastname: Shiomi
authors.forename: T
authors.initials: T
authors.lastname: Kuboyama
authors.forename: T
authors.initials: T
authors.lastname: Sawayanagi
authors.forename: H
authors.initials: H
authors.lastname: Nishigawa
authors.forename: S
authors.initials: S
authors.lastname: Kakizawa
authors.forename: S
authors.initials: S
authors.lastname: Miyata
authors.forename: M
authors.initials: M
authors.lastname: Ugaki
authors.forename: S
authors.initials: S
authors.lastname: Namba